It is even plausible that the gravitational effect is sub light scale by which i mean that it is less that the second dimension of a photon ribbon. Yet lining up particles allows this effect to be accumulated and it acts like the glue holding dark matter together as a non compressible fluid.
Such a non compressible fluid can just as obviously carry a wave created by a binary collapse. Now we need to set up equipment around the solar system to discover and even map the location of these events. I would also like to see light speed confirmed for this type of wave. That may not be true.